This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Hydrogels are networks of hydrophilic polymer chains and can contain over 90% wt. water. Most hydrogel materials are very weak due to their high water contents. Our research group has developed a hydrogel material with both high water content (70-90%wt.) and high tensile strength. Our material consists of a poly(ethylene glycol) network interpenetrated with a crosslinked network of poly(acrylic acid). Upon formation of this interpenetrating polymer network, tensile modulus and stress at fracture increase by an order of magnitude compared to single networks of each polymer. We are interesting in using SAXS measurements to probe the structure of our interpenetrating polymer networks. These measurements will give us valuable information regarding the nature of the observed increase in mechanical strength as well as the polymer network mesh size. This structural data can be related directly to our experimentally observed mechanical and transport properties. An understanding of the mechanisms responsible for the enhanced strength of these IPN hydrogels will provide insights on how to synthesize high strength synthetic soft tissue replacements.